KINETIC THEORY Kinetic Theory states that the tiny

KINETIC THEORY § Kinetic Theory states that the tiny particles in all forms of matter are in constant motion. § Kinetic refers to motion § Helps you understand the behavior of solid, liquid, and gas atoms/molecules as well as the physical properties § Provides a model behavior based off three principals

KINETIC THEORY § 3 Principles of Kinetic Theory § All matter is made of tiny particles (atoms) § These particles are in constant motion § When particles collide with each other or the container, the collisions are perfectly elastic (no energy is lost)

SOLIDS § § § Particles are tightly packed and close together Particles do move but not very much Definite shape and definite volume (because particles are packed closely and do not move) § Most solids are crystals § Crystals are made of unit cells (repeating patterns) § The shape of a crystal reflects the arrangement of the particles within the solid

SOLIDS § Unit cells put together make a crystal lattice (skeleton for the crystal) § Crystals are classified into seven crystal systems: cubic, tetragonal, orthorhombic, monoclinic, triclinic, hexagonal, rhombohedral § Unit cell crystal lattice solid

SOLIDS § Amorphous Solid: § A solid with no defined shape (not a crystal) § A solid that lacks an ordered internal structure § Examples: Clay, Play. Doh, Rubber, Glass, Plastic, Asphalt § Allotropes: § Solids that appear in more than one form § 2 or more different molecular forms of the same element in the same physical state (have different properties) § Example: Carbon § § § Powder = Graphite Pencil “lead” = graphite Hard solid = diamond

SOLIDS www. ohsu. edu/research/sbh/resultsimages/crystalvsglass. gif

LIQUIDS § § § Particles are spread apart Particles move slowly through a container No definite shape but do have a definite volume Flow from one container to another Viscosity – resistance of a liquid to flowing § Honey – high viscosity § Water – low viscosity chemed. chem. purdue. edu/. . . /graphics

GASES § § § Particles are very far apart Particles move very fast No definite shape and No definite volume http: //www. phy. cuhk. edu. hk/contextual/heat/tep/ trans/kinetic_theory. gif

GASES AND PRESSURE § Gas pressure is the force exerted by a gas per unit surface area of an object § Force and number of collisions § When there are no particles present, no collisions = no pressure = vacuum § Standard Pressure is average normal pressure at sea level § As you go ABOVE sea level, pressure is less § As you go BELOW sea level, pressure is greater

GASES AND PRESSURE § Standard Pressure Values § At sea level the pressure can be recorded as: § § § 14. 7 psi (pounds per square inch) 29. 9 in. Hg (inches of Mercury) 760 mm. Hg (millimeters of Mercury) 760 torr 1 atm (atmosphere) 101. 325 k. Pa (kilopascals) § All of these values are EQUAL to each other: § § 29. 9 in. Hg = 101. 325 k. Pa 760 torr = 760 mm. Hg 1 atm = 14. 7 psi and so on………. § Say hello to Factor Label Method!!!!!!

GASES AND PRESSURE § STP § Standard Temperature and Pressure § Standard Pressure values are the values listed on the previous slides § Standard Temperature is 0°C or 273 K § If temperature is given to you in Farenheit, must convert first! § °F = (9/5)°C + 32 § °C = (5(°F-32)) / 9 Remember order of operation rules § K = 273 + °C § °C = K – 273

TEMPERATURE § Temperature is the measure of the average kinetic energy of the particles. § 3 Units for Temperature: § Celsius § Farenheit § Kelvin § Has an absolute zero § Absolute lowest possible temperature § All particles would completely stop moving § Temperature Conversions: § Example 1: Convert 35°C to °F § Example 2: Convert 300 Kelvin to °C

KINETIC ENERGY AND TEMPERATURE § § § Energy of motion Energy of a moving object Matter is made of particles in motion Particles have kinetic energy KE = (mv 2)/2 OR KE = (ma)/2 § Kinetic Energy is measured in Joules § 1 J = 1 kg • m 2/s 2 § The mass must be in kg § The velocity must be in m/s OR acceleration must be in m 2/s 2

KINETIC ENERGY AND TEMPERATURE § Temperature-measure of the average kinetic energy of the particles § Kelvin Scale: § Has an absolute zero (0 K) § Absolute lowest possible temperature § In theory, all particles would completely stop moving § Speed of Gases: § If two gases have the same temperature (particles moving at the same speed) how can you tell which gas has a greater speed? § The only difference is mass! § To find mass, use the periodic table

KINETIC ENERGY AND TEMPERATURE § Speed of Gases § Example 1: If CH 4 and NH 3 are both at 284 K, which gas has a greater speed? § Step One: Add up the mass of each gas using the periodic table. § Step Two: The lighter gas moves faster (think about a race between a 100 -pound man and a 700 -pound man, the lighter man would move faster) § Example 2: Which gas has a faster speed between Br 2 and CO 2 if both are at 32°F?